1 dozen of eggs

1 pair of kicks (shoes)

One 2L of cola

reams of paper

So what unit do chemists use

to count particles?

Particles are so tiny, chemists use the unit of moles. A mole contains 6.02 x 1023 atoms.

602, 000, 000, 000, 000, 000, 000, 000

602,000,000,000,000,000,000,000• One mole of popcorn would cover every

dry surface of the Earth to a depth of six miles

• One mole of stacked pennies would reach to the moon and back 16 times

• One mole of marshmellows would cover the US to a depth of 650 miles

• 1811- Avogadro- equal volumes of gases at the same temperature and pressure contained equal number of molecules

• 1861- Cannizzaro- developed atomic weights for known elements

• 1865- Loschmidt- determined the number of atoms present in given volume of air

• 1971- true value 6.02 x 1023 found

Recall the Law of Conservation of Mass

Mass of reactants = mass of productsMass of starting substances = mass of ending substances

2 hydrogen atoms + 1 oxygen atom 1 water molecule

Law of Definite Proportions• Regardless of amount, a compound will always

be composed of the same elements in the same proportions by mass

• For example, two hydrogen atoms will always combine with one oxygen atom to produce one molecule of water

Moles Particles Conversion(particles could be atoms or molecules)

• If you have three and a half dozen roses, how many roses do you have?

• What is the conversion factor?

dozen

roses

dozen

roses

withstartyouunit

wantyouunit

1

12

rosesdozen

rosesx

dozen42

1

125.3

Moles Particles Conversion

mole

particlesx

1

1002.6 23

particlesx

mole231002.6

1

Particles Moles Conversion

withstartyouunit

wantyouunit

Convert 3.5 moles to atoms

Moles to atoms conversion factor

3.5 moles x 6.02x1023 atoms = 2.12 x 1024 atoms

1 mole

mole

particlesx

1

1002.6 23

Convert 18.06x1023 atoms to moles

• Atoms to moles conversion factor

• 18.06x1023 atoms x 1 mole = 3 moles

6.02x1023 atoms

particlesx

mole231002.6

1

Convert from moles to particles

• 2.7 moles of lithium

2.7 moles x 6.02x1023 particles

1 mole

= 1.625 x 1024 atoms

• 1.8 moles of sodium chloride

1.8 moles x 6.02x1023 particles

1 mole

= 1.08 x 1024 molecules

mole

particlesx

1

1002.6 23

Convert from moles to particles

• 5.3 moles of bromine

5.3 moles x 6.02x1023 particles

1 mole

= 3.19 x 1024 atoms

• 4.7 moles of potassium oxide

4.7 moles x 6.02x1023 particles

1 mole

= 2.83 x 1024 molecules

mole

particlesx

1

1002.6 23

particles moles

• 4.32 x 1024 atoms of calcium

4.32 x 1024 atoms x 1 mole

6.02 x 1023 atoms

BE CAREFUL WITH PARENTHESIS IN YOUR CALCULATOR!

= (4.32 x 10(24)) / (6.02 x 10(23))

= 7.18 moles of calcium

particlesx

mole231002.6

1

particles moles

• 2.7 x 1020 atoms of copper

2.7 x 1020 atoms x 1 mole

6.02 x 1023 atoms

= (2.7 x 10(20)) / (6.02 x 10(23))

= 0.0004485 moles of copper

=4.49 x 10-4 moles of copper

particlesx

mole231002.6

1

particles moles

• 2.5 x 1024 molecules of sodium chloride

2.5 x 1024 atoms x 1 mole

6.02 x 1023 atoms

=4.15 moles of sodium chloride

• 5.32 x 1023 molecules of calcium chloride

5.32 x 1023 atoms x 1 mole

6.02 x 1023 atoms

=0.88 moles of calcium chloride

particlesx

mole231002.6

1